It is known to generate gas superpressure in the space defined by the two king rolls and the partially produced winding and a lower seal and end walls, in order to achieve a winding structure that is as uniform as possible and that minimum winding errors with rolls to be wound that become increasingly heavier, which, with increased diameter, completely compensates for the increase in weight (DE-GM 92 01 791; DE-PS 1,047,001; DE-PS 1,111,496; U.S. Pat. No. 3,497,151; U.S. Pat. No. 3,346,209; WO 92/03366; DE 4,110,047 A1).
As is especially clear from DE 4,110,047 A1, which is hereby incorporated by reference in the disclosure of the present invention, it is required in these pneumatic support devices that both the winding space above the smallest gap of the support rollers and the winding space below it be sealed, forming a wind box (or blast box) with, for example, applied compressed air. For sealing the lower winding region, the winding box has side walls in the form of circular segments, which are adapted in shape to the external cross section of the two king rolls in such a way that between the outer surfaces of the wind box and a circular arc of each king roll, there remain uniform gaps that are as small as possible. The web to be wound passes advantageously through one of these two gaps. Although the two king rolls are arranged stationary, the long length of the king roll, which can exceed 8 or 10 m, imposes high requirements on the exact placement of the gaps between the king rolls and the parallel portions of the side walls of the wind box, which gaps are to be as small as possible. Since in changing a roll or threading in a new web to be wound, the gap between the enclosed king rolls and wind box is too small, it is envisioned according to DE 4,110,047 A1 that the wind box be swung away downward by means of an arm mechanism provided around a king roll around which the web is wound. Moving the whole wind box imposes significant requirements on the positioning of the wind box in the working position in order to avoid an air gap between the wind box that is on the one hand neither too large, i.e. requiring the use of high air pressure, nor on the other hand too small, causing occasional contact when moved.
Sealing of the upper winding space is only required at its two ends, but here the problem to be overcome is that the available sealing surface has a relatively small area, which makes a contact-free sealing with the least possible pressure loss more difficult. The sealing surfaces provided for the sealing task can only be brought into position when the roll being formed has reached a diameter large enough that the sealing surfaces can be swung between the winding core guidance device and one of the king rolls. This is only possible beginning with a relatively large winding diameter, because of the significant width of the upper spandrel space. In addition, it requires the upper and lower parts of the wind box to be separately swingable and the separation plane to be positioned at the tightest position between the king rolls, which further increases the sealing problem.